The first Macintosh operating system to have cooperative multitasking. While cooperative multitasking made its debut in system 4, it was not as seamless or integrated into the Finder but rather a program called Switcher. Cooperative multitasking relies on programs to relinquish control of the CPU. Modern operating systems now use preemptive multitasking, which do not rely on the programs but rather the OS to control who can execute. If a program was ill behaved or unwilling to relinquish the cpu then no other program could run until that program ended or forced to quit.

While Apple added the Multifinder, it was optional and at startup the user could select the Finder for non multitasking environment (faster if you only need to run one program) or MultiFinder (more efficient when needing to run multiple programs but more resource intensive.

Improvements:

System 6 added color support, though the Finder itself didn’t use color.

Disk was enhanced with a progress dialog with a Cancel button.

Get Info was enhanced to show the version number of a file.

Notification Monitor allowed programs to notify the user through the menu bar if they needed input

Systems 6.0.1-6.0.8 Added support for new models as they were released.